It has been proposed to use an electronic lock instead of a mechanical combination lock on secure enclosures such as safes and filing cabinets. However, a serious problem exists if the electronic lock fails in that there is no way to open the enclosure until the electronics have been repaired. If the failed electronic components are located within the locked enclosure, the only recourse is to torch the enclosure open.
In the copending application of myself and Walter Henderson entitled "Electronic Real Estate Lockbox System," Ser. No. 831,601, filed Feb. 21, 1986, and in my copending application entitled "Electronic Door Lock and Key," Ser. No. 814,364, filed Dec. 30, 1985, electronic lock systems are disclosed having a number of advantages that would be useful in connection with a lock for an enclosure such as a safe. For instance, the systems of the copending applications include a number of unique electronic keys. The systems are such that whenever a key is used, the identity of each key is recorded, together with its date and time of access, in an electronic memory so that a log can be kept of the keys used to gain access to the lock.
My present invention comprises modifying a more or less standard small safe lock, such as that disclosed in U.S. Pat. No. 3,968,667 to Gartner, issued July 13, 1976, so that it can additionally be unlocked by an electronic system, such as is disclosed in the above referenced copending applications.
More specifically, the preferred embodiment of my invention contemplates the provision of a socket or nest on the dial ring of a safe's combination lock, the socket being designed to receive an electronic key. I have modified the combination lock in such a manner as to make use of some of the lock's existing mechanical parts, but have modified these parts so as to enable the lock to be opened by use of a number of differently coded electronic keys. I have so designed the interrelationship of the electronics and the mechanics to provide a fail safe arrangement, so that in the event of a failure in the electronic lock circuitry, the safe can nevertheless be opened by entering the mechanical combination in the normal fashion.
I contemplate that only one person, probably an official of a firm, have knowledge of the safe's mechanical combination. Thus, no one can open the lock via the mechanical combination except that selected person. However, the employees who have reason to gain access to the safe can do so by making use of their individual electronic keys, each of which accesses is recorded in the lock's electronic access log.